Main requirements for an automobile wiper blade are shown in FIG. 1. A sector in FIG. 1 denotes a wiping region over which the wiper blade sweeps on a windshield glass. In the wiping region, a main visual region indicated by a symbol V is a region a driver is desired farthest to view clearly, and two side visual regions indicated by a symbol V′ are regions the viewing requirement for which is lower. When wiping is performed, a surface of the glass over which the wiper blade has swept should be fully wetted by water and a water film good in perspectivity is formed thereon. There should not be a dry region like a painted face unwetted by water. The water film need to be very thin and rainwater should not be accumulated into drips and flows down like tears. Also, water lines consistent with the arched locus in which the wiper blade sweeps should not arise. In regard to evaluation for wiping effect of the wiper blade, it is superior that the water line does not appear in both the V region and the V′ regions; it is superior secondly that the water line appears slightly only in the V′ regions; and it is inferior that there are more water lines.
In order to attain a high quality wiper blade, it has been found that better wiping effect can be achieved if pressure applied to the windshield glass along an entire length of the wiper blade is distributed evenly. In FIGS. 2A and 2B, a horizontal coordinate denotes a position in the length of the wiper blade wherein 0 is a center of the wiper blade and both ends of the wiper blade are located on left and right sides of the center, and a vertical coordinate denotes linear pressure P (represented by N/m or N/cm), i.e. the force due to pressure received by the glass over a unit length of the wiper blade, applied to the surface of the glass by the wiper blade. Compared with a curve C-2 in FIG. 2B, a curve C-1 in FIG. 2A shows that the linear pressure applied by the wiper blade is distributed more evenly and that better wiping effect can be obtained actually.
A wiper arm is connected to a connector provided on a central portion of the wiper blade only on an end thereof, that is, force is applied to the wiper blade only at the connection point. It is difficult to evenly distribute the force applied at the one point to the windshield glass via a rubber strip having a length of 40˜70 cm through a long strip beam or skeleton. The present invention achieves satisfactory effect by employing a specific structure of the wiper blade.